1. Field of the Invention
The present invention relates to a communication system provided for moving objects, and more particularly, to a method for displaying the current position of a moving object in a navigation device in accordance with the position condition of the moving object such that the indication of the position when the moving object is positioned on the ground is different from that when the moving object is positioned under the ground.
2. Description of the Related Art
A positioning device including a global positioning system (GPS), which is incorporated in a variety of moving objects such as vessels, aircraft and vehicles, to identify the current position and moving speed of the moving object while determining a movement path of the moving object, is well known. Such a GPS positioning device receives electrical waves, indicative of the latitude, longitude and altitude associated with the current position of a moving object, from a plurality of artificial satellites included in the GPS, thereby computing the current position of the moving object. After the computation, the GPS positioning device provides map information, including the current position of the moving object, to the driver of the moving object in the form of a graph. In other words, such a conventional navigation device indicates the current position of the moving object, which is calculated based on the navigation information received from the artificial satellites, on a map read from an auxiliary memory unit such as a CD-ROM and displayed on a display screen.
The navigation device also indicates the advancing direction of the moving object, the distance between the current position of the moving object and the destination of the moving object, the current speed of the moving object, the movement path of the moving object set by the driver prior to the running of the moving object, information about roads associated with the movement path, and an optimum movement path leading to the destination, etc., thereby providing a variety of information necessary to the running of the moving object to the driver.
However, conventional navigation devices display a running vehicle or moving object on a display screen by the same figure and color whether the running vehicle or moving object is positioned on the ground or under the ground. When the running vehicle or moving object is positioned under ground, it cannot be viewed from the sky because it is shielded by underground roads, elevated roads or buildings. In this case, navigation information from the GPS cannot be accurately received. However, the driver may not be aware that the moving object is underground and therefore the reception of the navigation information is poor.